1. Technical Field
The present invention relates to a spindle motor.
2. Description of the Related Art
Generally, a spindle motor, which belongs to a brushless-DC motor (BLDC), has been widely used as a laser beam scanner motor for a laser printer, a motor for a floppy disk drive (FDD), a motor for an optical disk drive such as a compact disk (CD) or a digital versatile disk (DVD), or the like, in addition to a motor for a hard disk drive.
Recently, in a device such as a hard disk drive requiring high capacity and high speed driving force, in order to minimize generation of noise and non repeatable run out (NRRO), which is vibration generated at the time of use of a ball bearing, a spindle motor including a fluid dynamic pressure bearing having lower driving friction as compared to an existing ball bearing form has been generally used. In the fluid dynamic pressure bearing, a thin oil film is basically formed between a rotor and a stator, such that the rotor and stator are supported by pressure generated at the time of rotation. Therefore, the rotor and stator are not in contact with each other, such that frictional load is reduced. In the spindle motor using the fluid dynamic pressure bearing, lubricating oil (hereinafter, referred to as an ‘operating fluid) maintains a shaft of the motor rotating a disk only with dynamic pressure (pressure returning fluid pressure to the center by centrifugal force of the shaft). Therefore, the spindle motor using the fluid dynamic pressure bearing is distinguished from a ball bearing spindle motor in which the shaft is supported by a shaft ball made of iron.
When the fluid dynamic pressure bearing is used in the spindle motor, the rotor is supported by the fluid, such that a noise amount generated in the motor is small, power consumption is low, and impact resistance is excellent.
However, in the spindle motor using the fluid dynamic pressure bearing according to the prior art, various problems such as scattering, or the like, of the operating fluid according to sealing of the operating fluid in the fluid dynamic pressure bearing have been generated. Particularly, an interface of the operating fluid, that is, an oil interface in the case in which oil is used as the operating fluid is significantly vulnerable to external impact, and the operating fluid is leaked to the outside due to impact, or the like, during operation. The leakage of the operating fluid deteriorates operating performance of the motor, thereby causing a serious problem such as deterioration in reliability of the motor operation.